1. Field of the Invention
The invention pertains to a vaccine prepared from a live, but attenuated virus of the Delaware strain inducing infectious bursal disease in chickens. Specifically, a vaccine is prepared by screening potential attenuated virus candidates with a non-neutralizing specific monoclonal antibody. Further, a highly specific neutralizing monoclonal antibody is provided as an alternative, effective vaccine.
2. Background of the Prior Art
In the inventors' related applications, including U.S. patent application Ser. No. 07/423,752, entitled MONOCLONAL ANTIBODIES FOR INFECTIOUS BURSAL DISEASE, VACCINES AND ASSAYS FOR USE THEREWITH, which in turn is a CIP application of U.S. application Ser. No. 07/061,083, now U.S. Pat. No. 4,956,452 and U.S. application Ser. No. 07/227,311, now U.S. Pat. No. 5,064,646 the development and study of a large number of monoclonal antibodies (Mab) specific for various strains of infectious bursal disease is discussed. As related in the above-cited U.S. application Ser. No. 07/423,752, the entire content of which is incorporated herein by reference, a panel of antibodies has been developed, each specific to a particular type of infectious bursal disease virus. That virus has been, by means of antibody assays, categorized into three separate classifications, classic, Delaware and GLS. At the time of filing of this application, the Delaware strain, of all pure strains, appears to be the dominant infectious bursal disease virus in the Eastern United States. Certainly, it is a substantial and continuing threat to the U.S. poultry industry.
Wild-type Delaware IBDV have been known for some time, and are commercially available. There are a number of vaccines for this Delaware-type IBDV commercially available, including both "killed" and "live" vaccines. A killed vaccine is prepared by culturing the virus itself, in e.g., chicken eggs and the like, and subsequently "killing" the virus by heat, chemical treatment and the like. In a live vaccine, the virus is present in a living form, but has been attenuated to reduce or eliminate its virulency, by serial passage through cell culturing and the like. Thus, the "virus" component of a live vaccine is attenuated. Methods for preparation thereof are known in the art, and do not constitute, per se, an aspect of this invention. No currently available vaccine for wild-type Delaware IBDV is based on or comprises a non-virus active element, such as a monoclonal antibody.
During the analysis and categorization of IBDV in the United States, all commercially available live, attenuated Delaware strain vaccines were assayed. One of the monoclonal antibodies used in that assay is designated BK9, and is expressed by the hybridomal cell line deposited at the ATCC under deposit number HB-10157.
It is apparent that in order to provide adequate coverage and protection against the Delaware strain infection, a live, attenuated vaccine must contain a virus that will produce antibodies recognizing the wild-type Delaware IBDV. That is, in the process of attenuation, the marker characteristics of the wild-type Delaware virus strain must not be lost. Surprisingly, in the course of testing commercially available vaccines, not one was demonstrated to bear the BK9 Mab marker, and thus not truly wild-type. Vaccines employing this type of virus will not, in fact, generate antibodies providing effective protection against wild-type Delaware IBDV infection. Thus, it remains a pressing need in the industry to provide a live, attenuated vaccine for Delaware IBDV.
Alternatively, it is known that for certain IBDV, vaccines can be prepared from monoclonal antibodies (Mab) which neutralize the virus. See, in particular, U.S. Pat. No. 4,956,452. It is a continuing goal to provide such Mab which neutralize the Delaware strain IBDV, and provide a vaccine based thereon.